PROJECT SUMMARY/ABSTRACT Physical inactivity, poor nutrition, and overweight/obesity are leading risk factors for cardiovascular disease, in youth and into adulthood. A better understanding of interplay between the behavioral, psychosocial, and environmental influences of obesogenic behaviors is needed to improve prevention efforts. Specifically, psychosocial and environmental factors appear to be important influencers of health behaviors in adolescents, but little is known about how they interact and the role of context-general vs. context-specific factors in and outside of school. For example, it is possible that context-general factors play only a small role in influencing behaviors in unsupportive environments, so context-specific psychosocial and environmental approaches may be needed in such circumstances. Furthermore, physical inactivity is related to energy intake dysregulation in adults, but less is known in adolescents. The present study will investigate the relative role and interplay between school and non-school settings, and context-general and context-specific (both psychosocial and environmental) factors in relation to youth's obesogenic behaviors (i.e., physical activity, sedentary time, and nutrition; Aim 1), and whether adolescents with low amounts of physical activity experience energy intake dysregulation (Aim 2). Participants (Aim 1 N=549; Aim 2 N=880) will be 11-17 year olds from two large metropolitan areas in the US. Participants completed surveys to capture psychosocial and perceived environment variables, and accelerometer assessments to capture physical activity, sedentary time, and sedentary patterns (e.g., interrupted vs. prolonged). A subsample wore a global positioning systems tracker to track time and physical activity in school and out of school. Geographic Information Systems assessed physical activity- and nutrition-related environmental factors in the home neighborhood. Direct observation measures assessed streetscapes and food quality inside food outlets around participants' homes. Statistical analyses will include comparing obesogenic behaviors and correlates (context-general and context-specific) of these behaviors between in-school and out- of-school time (Aim 1). Interactions between context-general and context-specific factors will be explored. For Aim 2, non-linear modeling to identify gender-specific thresholds of physical activity (minutes per day) needed to support energy intake regulation. If Aim 2 is supported, findings would inform the amount of emphasis placed on promoting physical activity in obesity prevention efforts and inform physical activity guidelines. For Aim 1, findings will advance understanding of whether and how to target both context-general and context-specific factors in supporting youth's health behaviors, and the relative potential for school-based vs. family-based interventions for supporting context-specific and overall health behaviors in youth. Findings will inform a larger study that will investigate this model in a wider range of settings relevant to youth's health behaviors to inform the development of interventions and policies to ultimately improve youth's overall health and development.